Manually-operated wheelchairs are well known. Most prior art manually-operated wheelchairs have been designed for two-handed operation by persons, as for example paraplegics, having full or partial use of both hands. Typically, a wheelchair is movably supported by two larger rear wheels and two smaller forward (generally swivel-type) wheels. These wheelchairs are manually-driven or operated by an occupant gripping top portions of the larger rear wheels (or hand-rim assemblies directly connected to the rear wheels) and then pushing the wheels in a desired direction to propel the wheelchair in a chosen direction. If an occupant desires to turn the wheelchair in a particular direction, the larger rear wheel on that side of the wheelchair relevant to the direction of turn is pushed more slowly than the opposite rear wheel, which gradually changes the direction of movement of the wheelchair. Sharp turns are generally accomplished by holding one rear wheel stationary whilst pushing the opposite rear wheel in a desired direction. In some cases both rear wheels are propelled in opposite directions to rotate the wheelchair sharply on-the-spot in a desired direction. The smaller forward wheels of the wheelchair generally swivel and follow the arc of rotation of the wheelchair directed by the propulsion applied to the rear wheels.
Two-handed manually operable wheelchairs usually include frames which are collapsible for transportation. A common design for a conventional collapsible two-handed wheelchair includes side-frames which are mounted to scissor-like cross-frame members which enable the opposing side-frames to be drawn together in close proximity to one another, which results in the overall dimensions of the wheelchair being substantially reduced. This collapsible configuration facilitates portability, ease of transportation and storage in, for example, the boot of a vehicle.
A disadvantage associated with one design for conventional two-handed manually-driven wheelchairs is that an occupant must use both arms to manoeuvre the wheelchair at all times. This is most disadvantageous when an occupant needs to carry an object from one point to another, for example from a refrigerator to a kitchen table. It is common practice in situations like this for a wheelchair occupant to balance any load he (or she) wishes to carry on his (or her) lap whilst manoeuvring the wheelchair with both arms.
A further disadvantage with known designs of conventional two-handed wheelchairs is due to the fact that, since they have two large rear drive wheels independently connected to the wheelchair frame, the muscle power of a single arm can only be delivered to a single drive wheel of the wheelchair. If a wheelchair occupant has one arm stronger than the other, the maximum effort in forward movement of the wheelchair is dependent on that of the weakest arm, otherwise the wheelchair would continually turn if uneven strength was to be continually applied to both wheels.
Some manually-driven wheelchairs have also been provided for single-handed operation by persons having use of only a single hand. Typically, single-handed manually-driven wheelchairs provide two individually operable and concentrically positioned hand-rim assemblies mounted on the working-hand side of the wheelchair. Each hand-rim assembly is adapted to drive one wheel of the wheelchair. A first hand-rim assembly is usually directly mounted to the rim of one large rear wheel of the wheelchair, whilst a second hand-rim assembly, generally located adjacent the first hand-rim assembly, is coupled to the opposite rear wheel and is operable in order to drive the opposite rear wheel from the working-hand side of the wheelchair. A single drive axle couples the hub of the rear wheel located on the non-working-hand side to the second hand-rim assembly located on the working-hand side. This arrangement of two hand-rim assemblies located on a single working-side enables an occupant to not only drive the rear wheel adjacent the working-hand, but also the opposite rear wheel located on the opposite side of the wheelchair by way of pushing both hand-rim assemblies together or separately in a desired direction. When both hand-rim assemblies are propelled together, the occupant is able to drive the wheel chair in a relatively straight line by using only a single hand.
One problem associated with single-handed manually-driven wheelchairs is that they are purposely designed for either left or right handed operation, and not both. Such wheelchairs usually require tooling to convert the wheelchair from left-handed drive to right-handed drive operation, depending on which arm an occupant is able to use. A further disadvantage with such prior art single-handed wheelchairs is that they are sometimes not collapsible or do not collapse to a sufficiently compact state, due to the rigid or semi-collapsible drive axle configuration interconnecting the second hand-rim assembly with the rear wheel located on the non-working-hand side of the wheelchair. Usually, in the case of rigid drive axles, the drive axle extends transverse to the side-frames of the wheelchair in a direction substantially parallel to the direction of collapse of what would normally be a conventional collapsible frame, which opposes the collapsible nature of the wheelchair.
Another disadvantage associated with most conventional manually-driven wheelchairs, both two-handed and single-handed operation, is that many wheelchair occupants do not have sufficient upper body strength to traverse inclines or other rugged terrain. The general set-up of a conventional wheelchair results in a 1:1 drive propulsion ratio. As such, many wheelchair occupants are limited in terms of their scope of mobility.
Wheelchair manufacturers tend to use small castor wheels as means for supporting and rotating the forward section of a wheelchair in response to force applied to the larger rear drive wheels. Castor wheels can easily become jammed or snagged against, for example, small ledges, edges of carpet and/or cracks in pavement. With conventional wheelchairs it is common practice to rotate both drive wheels forcefully in opposite directions in order to generate enough rotational force (on a 1:1 drive ratio) at the castor wheels to release the jammed wheel.
With conventional two-handed wheelchairs, when occupants try to traverse an incline they have to be sure that they quickly push, release, and then re-engage the wheels to push again, so as to be sure that the wheelchair does not slip backwards down the incline. If instead the wheelchair occupant tries to drive the wheelchair uphill by releasing one arm from one wheel at a time, the wheelchair will pivot and rotate backwards relative to the wheel that is being held firm. Thus, the only way to navigate a conventional two-handed wheelchair uphill is by way of pushing with both hands against both wheels simultaneously. It therefore becomes evident that, if an operator does not re-engage and push forward again on the wheels of the wheelchair in a manner which is quick enough dependent on the grade of the incline, the wheelchair will roll backwards down the incline.
It is therefore an object of the present invention to provide a manually-driven wheeled conveyance, preferably a wheelchair, which can be propelled and steered by either or both arms of an occupant.
A further object of the present invention is to provide a manually-driven wheeled conveyance, preferably a wheelchair, which can be propelled and steered by either hand of a two-handed person enabling an occupant to use the other hand to carry an object.
Yet a further object of the present invention is to provide a manually-driven wheeled conveyance, preferably a wheelchair, which can be propelled and steered by a single-handed person and which is configured for both left-handed and right-handed drive operation.